For these reasons heretofore, methods were essentially used in which specificity was insured by solvent extraction prior to the radioimmune assay. Solvent extraction interferes, however, with continuous and mechanized sample processing.
In experiments to simplify radioimmunological methods by way of solid phase techniques, antibodies were bonded covalently to different matrices, such as, e.g., agar, cellulose, glass particles, polyamides and polyacrylamides; see for example U.S. Pat. No. 3,793,445 to Updike et al. The advantages of antibodies enclosed in a matrix consist of the exclusion of interfering molecules of higher molecular weight, the savings of pipetting and centrifuging steps and the extended stability of the immobilized antibodies at room temperature.
It was found that the bonding specificity of the antibody, when immobilized in the known manner in a matrix, does not satisfy desirable requirements.